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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 250814A: COLIBRÍ optical upper limit
  2. GRB 250814B: Fermi GBM Final Real-time Localization
  3. GRB 250813A: AstroSat CZTI detection
  4. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  5. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  6. GRB 250814A: DDOTI Optical Upper Limit
  7. GRB 250813B: EP-FXT counterpart detection
  8. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  9. GRB 250813B: Swift-XRT afterglow detection
  10. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  11. GRB 250814A: Fermi GBM Final Real-time Localization
  12. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  13. GRB 250813B: Ondrejov D50 fast decay
  14. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  15. GRB 250813B: Ondrejov D50 optical afterglow detection
  16. GRB 250813B: SVOM detection of a bright long burst
  17. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  18. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  19. EP250812a: Nickel optical upper limit
  20. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  21. GRB 250812A: NTT spectroscopic redshift z = 2.57
  22. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  23. EP250812a: NOT, NTT, and GS observations
  24. GRB 250812A: Swift/UVOT Detection
  25. GRB 250813A: Fermi GBM Final Localization
  26. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  27. EP250812a: Liverpool Telescope upper limits
  28. EP250812a: SVOM/VT optical counterpart
  29. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  30. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  31. IceCube Alert 250813.14: Global MASTER-Net observations report
  32. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  33. GRB 250812A: EP-FXT counterpart detection
  34. GRB 250812A: Swift ToO observations
  35. GRB 250807B: Swift-BAT refined analysis
  36. EP 250812a: GOTO optical upper limit
  37. GRB 250812A: Kilonova-Catcher optical afterglow detection
  38. EP250812a: Swift-XRT counterpart detection
  39. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  40. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  41. EP250812a: Einstein Probe detection of an X-ray transient
  42. GRB 250812A: SVOM/VT optical afterglow confirmation
  43. GRB 250812A: Swift-XRT afterglow detection
  44. GRB 250812A: TRT likely optical counterpart detection
  45. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB 250812A: SVOM detection of a faint long burst
  47. GRB 250809A: Swift-BAT refined analysis
  48. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  49. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  50. GRB 250807A: Swift-BAT refined analysis
  51. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  52. GRB 250809A: Swift/UVOT Detection
  53. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  54. Corrected Swift-XRT Refined Analysis of GRB 250809A
  55. GRB 250809A: Swift-XRT refined Analysis
  56. GRB 250807B: SVOM/VT optical observation
  57. EP250807a: EP-FXT follow-up observation upper limit
  58. GRB 250809A: LCOGT Optical Upper Limits
  59. GRB 250702B: Chandra X-ray Detection
  60. EP250807a: Global MASTER-Net observations report
  61. Fermi GRB 250808A: Global MASTER-Net observations report
  62. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  63. GRB 250808A: VLT X-shooter candidate counterpart
  64. GRB 250809A: Prompt enhanced Swift-XRT position
  65. GRB 250809A: Swift detection of a gamma ray burst
  66. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  67. GRB 250808A: Fermi GBM Observation
  68. GRB 250808A: Swift-XRT candidate counterpart detection
  69. GRB 250807A: SVOM/VT optical continued observation
  70. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  71. GRB 250808A: SVOM detection of a long burst
  72. GRB 250808A: Fermi GBM Final Real-time Localization
  73. Konus-Wind detection of GRB 250807A
  74. GRB 250807B: Swift/UVOT Detection
  75. GRB 250807B: Kilonova-Catcher optical afterglow detection
  76. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  77. GRB 250807A: Swift/UVOT Detection
  78. GRB 250807A: Swift-XRT refined Analysis
  79. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  80. GRB 250806A: SVOM/MXT refined analysis
  81. GRB 250806A: SVOM/ECLAIRs refined analysis
  82. EP250807a: NTT z-band optical upper limit
  83. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  84. GRB 250804B: Insight-HXMT detection
  85. GRB 250807A: SVOM/GRM observation
  86. Swift GRB250807.45: Global MASTER-Net observations report
  87. GRB 250807A: AstroSat CZTI detection of bright long burst
  88. GRB 250807B: Swift-XRT refined Analysis
  89. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  90. GRB 250807B: NTT optical observations
  91. EP250807a: EP-WXT detection of a fast X-ray transient
  92. EP 250807.979: GOTO optical upper limit
  93. EP250807a: COLIBRÍ optical upper limit
  94. GRB 250807A: SVOM/VT optical observation
  95. EP250806a: Upper limit from Fermi-GBM Observations
  96. GRB 250807B: Enhanced Swift-XRT position
  97. Swift GRB250807.65: Global MASTER-Net observations report
  98. GRB 250807A: Enhanced Swift-XRT position
  99. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 250807B: Swift detection of a burst with an optical counterpart.

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